Digitally regulated power supply for use in electrostatic transfer reproduction apparatus

Abstract

A digitally regulated power supply for the corona charging unit of an electrostatic copying machine in which a sample of the ionic current of the corona unit is utilized in conjunction with a digital regulator to regulate the power supply establishing the charge of the corona. The digital regulator in conjunction with at least one pulse width modulated power supply permits very fast rise and fall times of the power supply current. Further, between duty cycles of the machine, the digital regulator stores a representation of the correct operating point of the corona charging unit determined in the immediately prior duty cycle. In the next duty cycle, the representation is utilized by the digital regulator to initially regulate the power supply.

What is claimed is: 
     
       1. In an electrophotographic machine of the type described, a method for rapidly supplying a predetermined voltage from a power supply to a charge corona unit, said method comprising the following steps: (a) preconditioning a digital regulator of the power supply to the nominal operating point for the corona voltage supplied to the charge corona unit;   (b) digitally controlling the power supply with the preconditioned regulator upon initial electrical connection of the power supply to the corona unit; and   (c) digitally dynamically regulating the power supply in accordance with variations of the corona provided by the charge corona unit after the power supply is electrically connected to the corona unit.   
     
     
       2. In an electrophotographic machine of the type described, a method for rapidly supplying a predetermined voltage from a power supply to a charge corona unit having at least first and second bays, said method comprising the following steps: (a) preconditioning a digital regulator of the power supply to provide a predetermined amount of electrical energy to said charge corona unit;   (b) utilizing said digital regulator, as preconditioned, to regulate the power supply to provide said predetermined amount of electrical energy to said charge corona unit when less than all of said at least first and second bays of said charge corona unit are electrically connected to said power supply; and   (c) utilizing said digital regulator to dynamically digitally regulate the amount of electrical energy provided to said charge corona unit, when all bays of said unit are electrically connected to the power supply.   
     
     
       3. In an electrophotographic machine a power supply system for charging a corona generating unit to provide an electrostatic charge on a photoconductor medium, said power supply system including: a corona generating unit adjacently positioned to a photoconductor medium to be electrically charged;   a controllable power supply means coupled to said corona generating unit and said photoconductor medium for impressing a direct current potential on said corona generating unit with respect to said photoconductor medium;   feedback circuit means coupled to said power supply means and said corona generating unit, said feedback circuit means dynamically providing a binary digital electrical manifestation indicative of whether the power supplied to the corona generating unit is below proper level, at proper level, or above proper level;   digital regulator means coupled to said feedback circuit means and said controllable power supply, said digital regulator means being responsive to said feedback circuit means and controlling said power supply means, to increase the power supplied to said corona generating unit when said feedback circuit means manifests that the power supplied to said corona generating unit is below the proper level, to maintain constant the power supplied to said corona generating unit when said feedback circuit means manifests that the power supplied to said corona generating unit is at the proper level, and to decrease the power supplied to said corona generating unit when said feedback circuit means manifests that the power supplied to said corona generating unit is above the proper level;   and said digital regulator means being characterized by the inclusion of a single UP/DOWN counting means responsive to said electrical manifestation from said feedback circuit means, a source of periodic pulses, first counting means connected to said source of periodic pulses, second counting means coupling said first counting means to said UP/DOWN counting means, comparator means for comparing the count of said first counting means with the count of said UP/DOWN counting means and logical circuit means including bistable circuit means, said logical circuit means interconnecting said first counting means and said comparator means with said controllable power supply means.   
     
     
       4. In an electrophotographic machine, a power supply system as recited in claim 3 further characterized in that said corona generating unit includes a grid and said feedback circuit means comprises a serial circuit including, in the order recited, said grid of said corona generating unit, a low pass filter circuit and a threshold detector circuit. 
     
     
       5. In an electrophotographic machine wherein an electrical charge is selectively impressed on a moving photoconductor medium by controllably generating a corona discharge between a corona generating device and said moving photoconductor medium, a charge corona power supply means said charge corona power supply means comprising: a moving photoconductor medium;   a corona generating device having a first bay and a second bay encompassed by a shield, said first and second bays each including at least one corona generating wire, said corona generating device being positioned adjacent said photoconductor medium and having a grid positioned between said corona generating wires and said photoconductor medium;   a controllable first pulse width modulated power supply for providing a DC potential on said at least one corona wire of said first bay of said corona generating device;   a controllable second pulse width modulated power supply for providing a DC potential on said at least one corona wire of said second bay of said corona generating device;   connection means including resistance means, and a DC potential source, said connection means interconnecting said first and second pulse width modulated power supplies, to said corona wires, said shield, and said grid of said corona generating device, and said photoconductor medium;   said connection means including a node for providing a feedback signal indicative of the electrical charge impressed on said photoconductor medium;   feedback circuit means consisting essentially of a low pass filter and a threshold detector, said feedback circuit means being connected to said node of said connection means, said feedback circuit means accepting said feedback signal indicative of the electrical charge impressed on said photoconductor medium and providing a binary signal having first, second and third discrete states respectively manifesting that the electrical charge placed on said photoconductor is below a desired level, at a desired level, or above a desired level;   digital regulator means including a single UP/DOWN counter, said digital regulator means being coupled to said feedback circuit means and said first and second pulse width modulated power supplies, said digital regulator means regulating the duty cycle of said first and second power supplies respectively in accordance with said first, second and third binary signals from said feedback circuit means;   whereby the duty cycle of said first and second power supplies is (1) increased in response to said first binary signal, (2) maintained constant in response to said second binary signal, and (3) decreased in response to said third binary signal.   
     
     
       6. In an electrophotographic machine wherein an electrical charge is selectively impressed on a moving photoconductor medium by controllably generating a corona discharge between a corona generating device and said moving photoconductor medium, a charge corona power supply means said charge corona power supply means comprising: a moving photoconductor medium;   a corona generating device having a first bay and a second bay encompassed by a shield, said first and second bays each including at least one corona generating wire, said corona generating device being positioned adjacent said photoconductor medium and having a grid positioned between said corona generating wires and said photoconductor medium;   a controllable first pulse width modulated power supply for providing a DC potential on said at least one corona wire of said first bay of said corona generating device;   a controllable second pulse width modulated power supply for providing a DC potential on said at least one corona wire of said second bay of said corona generating device;   connection means including resistance means, and a DC potential source, said connection means interconnecting said first and second pulse width modulated power supplies, to said corona wires, said shield, and said grid of said corona generating device, and said photoconductor medium;   said connection means including a node for providing a feedback signal indicative of the electrical charge impressed on said photoconductor medium;   feedback circuit means connected to said node of said connection means, said feedback circuit means accepting said feedback signal indicative of the electrical charge impressed on said photoconductor medium and providing a binary signal having first, second and third discrete states respectively manifesting that the electrical charge placed on said photoconductor is below a desired level, at a desired level, or above a desired level;   digital regulator means coupled to said feedback circuit means and said first and second pulse width modulated power supplies, said digital regulator means regulating the duty cycle of said first and second power supplies respectively in accordance with said first, second and third binary signals from said feedback circuit means;   wherein said digital regulator means is characterized by the inclusion of,   a binary counter having a radix of 2 n  where n is an integer greater than 2 said binary counter having an input and an output, a source of periodic pulses connected to said input of said binary counter, an UP/DOWN binary counter having a radix of 2 n , said UP/DOWN binary counter having an input and control means for directing said UP/DOWN counter to count UP, maintain its count constant, or count DOWN, said control means of said UP/DOWN binary counter being connected to said feedback circuit means and responsive to said first, second and third discrete binary states of said binary signal provided by said feedback circuit means, delay circuit means having an input connected to said output of said binary counter and an output connected to said input of said UP/DOWN counter, a binary comparator coupled to said binary counter and said UP/DOWN binary counter, said comparator having an output and providing a signal thereon when said count in said binary counter equals said count in said UP/DOWN counter, a toggle flip-flop having an input, a first output and a second output, said input of said toggle flip-flop being connected to said output of said binary counter, said first and second outputs of said toggle flip-flop providing complementary outputs, a set-reset flip-flop having a set input, a reset input and an output, said set input of said set-reset flip-flop being connected to said output of said binary counter, said reset input being connected to said output of said binary comparator, and logical circuitry coupling said first and second outputs of said toggle flip-flop and said output of said R-S flip-flop to said first and second pulse width modulated power supplies;   whereby the duty cycle of said first and second power supplies is (1) increased in response to said first binary signal, (2) maintained constant in response to said second binary signal, and (3) decreased in response to said third binary signal.   
     
     
       7. In electrostatic transfer reproduction apparatus utilizing a digitally regulated power supply for charging a corona charging unit, a method of rapidly and efficiently arriving at the optimum corona level for properly electrically charging the transfer medium, said method comprising the following steps: (a) placing a specific control number from a range of control numbers in a digital regulator to regulate a corona power supply to provide a predetermined amount of energy to said corona charging unit;   (b) continuously sensing the electrical characteristics of the corona provided by said corona charging unit to determine whether said predetermined amount of energy is (1) too low in amount, (2) proper in amount, or (3) too high in amount;   (c) continuously appropriately modifying said control number, up or down incrementally, as the case may be, only if the amount of energy supplied to said corona charging unit was determined in step (b) to be too low or two high;   said method being characterized in that upon completion of step (a), steps (b) and (c) are not undertaken until all bays of a multi-bay corona charging unit have been energized.   
     
     
       8. In electrostatic transfer reproduction apparatus utilizing a digitally regulated power supply for a charging a corona charging unit the method of claim 7, wherein the specific control number utilized in step (a) is the final control number arrived at in step (c) of the immediately prior duty cycle employing the method of claim 7. 
     
     
       9. A method for regulating a power supply means employed in an electronic control system having a digital regulator and at least first and second portions energizable in the order recited, said method comprising the following steps: (a) upon turn on of said first portion of said control system, preconditioning said digital regulator to provide a nominal operating condition for said power supply means;   (b) utilizing said digital regulator as preconditioned to regulate said power supply means until all of said at least first and second portions of said control system are energized; and   (c) upon full energization of said power supply means permitting said digital regulator to dynamically regulate said power supply means.   
     
     
       10. A method for regulating a power supply means as recited in claim 9 wherein subsequent to step (c) said control system is turned off and said digital regulator maintains its then current status to be utilized as the afore recited preconditioning of the digital regulator upon subsequent turn on of the control system. 
     
     
       11. In apparatus utilizing a digitally regulated power supply for providing energy to a load unit, a method of rapidly and efficiently arriving at the optimum energy level proper operation of said apparatus, said method comprising the following steps: (a) placing a specific control number from a range of control numbers in a digital regulator to regulate a power supply to provide a predetermined amount of energy to said load unit;   (b) continuously sensing the electrical characteristics of said load unit to determine whether said predetermined amount of energy is (1) too low in amount, (2) proper in amount, or (3) too high in amount;   (c) continuously appropriately modifying said control number, up or down incrementally, as the case may be, only if the amount of energy supplied to said load unit was determined in step (b) to be too low or two high;   said method being characterized in that upon completion of step (a), steps (b) and (c) are not undertaken until all portions of the load unit have been energized.   
     
     
       12. In electrostatic transfer reproduction apparatus utilizing a digitally regulated power supply for providing energy to a load unit the method of claim 11, wherein the specific control number utilized in step (a) is the final control number arrived at in step (c) of the immediately prior duty cycle employing the method of claim 11. 
     
     
       13. In a machine, a method for rapidly supplying an optimum energy level from a power supply to a utilization unit, said method comprising the following steps: (a) preconditioning a digital regulator of the power supply to the nominal operating point for the utilization unit;   (b) digitally controlling the power supply with the preconditioned regulator upon initial electrical connection of the power supply to the utilization unit; and   (c) digitally dynamically regulating the power supply in accordance with variations of the utilization unit after the power supply is electrically connected to the utilization unit.